It is proposed to study the basic structure-function relationships of reconstituted membranes obtained from well-defined lipids and proteins. The interactions will be studied with techniques involving: diffusion measurements through vesicles, differential scanning calorimetry and enzyme assays. The protein of particular interest: proteolipid apoprotein from myelin, basic myelin protein, (Na plus K) stimulated ATPase. The role of lipid fluidity and cholesterol will be evaluated.